Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 35: Postersession Transport: Nanoelectronics, Quantum Coherence and Quantum Information, Fluctuations and Noise

TT 35.33: Poster

Mittwoch, 25. März 2009, 14:00–18:00, P1A

Full Counting Statistics of Interacting Quantum Dots with Ferromagnetic Leads — •Stephan Lindebaum, Daniel Urban, and Jürgen König — Theoretische Physik, Universität Duisburg-Essen, 47048 Duisburg, Germany

We investigate the full counting statistics of electronic transport through a single-level quantum dot weakly coupled to two leads. In the systems under consideration either one or both leads are ferromagnetic. For both situations we study the influence of the two spin channels on the transport properties to identify several underlying transport processes.

Starting from a generalized master equation we use a diagrammatic real-time theory to calculate the cumulant generating functions to first order in the tunnel coupling strength [1]. In the case of two ferromagnetic leads and strong Coulomb interaction an exchange field between dot and leads exists, which leads to a precession of the accumulated dot spin [2].

The interaction of dot electrons crucially affects the cumulants. If both leads are ferromagnetic the cumulants show a non-trivial dependence on the angle between the magnetization directions of the leads. They become strongly super Poissonian and may even diverge for high polarizations. Furthermore, they exhibit sign changes in dependence of the polarization angle. With only a single ferromagnetic lead it turns out that the majority electrons govern the statistics of the system.

[1] A. Braggio et al. , Phys Rev. Lett. 96, 026805 (2006).

[2] M. Braun et al. , Phys. Rev. B 70, 195345 (2004).